The present invention relates to an environrimental protection apparatus for an optical assembly of a type that uses bulk optics in an optical path. The present invention also relates to a method of manufacturing an environmental protection apparatus for an optical assembly.
It is well known that both the operational efficiency and the working lifetime of an optical assembly are dependent upon the environmental conditions within which the optical assembly operates. Contaminants such as non-inert gases or moisture that come into contact with parts of the optical assembly can cause degradation and/or irreparable damage of the parts of the optical assembly.
FIG. 1 is a schematic diagram of a known package used in the art to provide environmental protection for an optical assembly. The optical assembly is substantially hermetically sealed within a housing 10 by a lid 8 to create a substantially hermetically sealed package containing a controlled gas environment 11 therein. The optical assembly comprises a bulk optical component 12 formed from a polymer such as polycarbonate and through which electromagnetic radiation 13, typically light, can propagate. The bulk optical component 12 comprises a reflecting surface 14 (by virtue of total internal reflection) which is substantially planar in shape and a lens portion 16. The optical assembly also comprises an optoelectronic device 18 disposed adjacent and beneath the lens portion 16 of the bulk optical component 12.
In operation, electromagnetic radiation 13 is divergent on leaving an optical fibre (not shown) and when entering the bulk optical component 12. The electromagnetic radiation 13 is incident upon the reflecting surface 14 and, via total internal reflection of the electromagnetic radiation 13, the electromagnetic radiation 13 is reflected to the lens portion 16. The lens portion 16 focuses the electromagnetic radiation 13 onto the optoelectronic device 18.
Although a near contaminant free, controlled, gas environment 11 can be achieved by the near-hermetic seal between the lid 8 and the housing 10, some ingress of contaminants and moisture into the sealed package will occur as the seal is not perfect. Similarly, if the near-hermetic seal between the lid 8 and the housing 10 fails, ingress of non-inert gases and moisture into the housing will occur, thereby contaminating the controlled gas environment 11 of the package. Consequently, over time, the performance of the optical assembly degrades and the bulk optical component 12 and the optoelectronic device 18 become damaged due to the ingress of contaminants. Furthermore, production of the near-hermetically sealed package having the controlled gas environment 11 is costly and time consuming. Also, the location of the optoelectronic device 18 beneath the lens portion 16 of the bulk optical component 12 makes visual alignment of the optoelectronic device 18 with the bulk optical component 12, so that the electromagnetic radiation 13 is incident upon the optoelectronic device 18, very difficult due to the bulk optical component 12 obscuring the view of the optoelectronic device 18. The difficulty in visual alignment of the bulk optical component 12 with the optoelectronic device 18 increases the time and costs associated with the production of the packaged optical assembly.
According to the present invention, there is provided a package for an optical assembly comprising an optoelectronic device, characterised in that the bulk optical component and the optoelectronic device are enveloped by an encapsulant material having a substantially same refractive index as the bulk optical component, the bulk optical component having a reflective surface to, when in use, reflectively direct electromagnetic radiation incident thereupon to the optoelectronic device.
Preferably, the encapsulant material is silicone.
Preferably, the reflective surface is curved so as to focus the electromagnetic radiation. More preferably, the reflective surface is metallised.
According to the present invention, there is also provided a method of forming a package for an optical assembly, the method comprising the steps of: disposing an optoelectronic device on a substrate; aligning the bulk optical component with respect to the optoelectronic device, the optoelectronic device not being obscured by the bulk optical component during the alignment of the bulk optical component with the optoelectronic device; enveloping the bulk optical component and the optoelectronic device with an encapsulant material; and depositing a protective layer over the encapsulant material.
It is thus possible to provide a packaged optical assembly with effective environmental protection of the parts of the optical assembly by the envelopment of the optical assembly with silicone. Furthermore, visual alignment of the optoelectronic device with the bulk optical component, so that the electromagnetic radiation is incident upon the optoelectronic device, is simplified due to the position of the optoelectronic device relative to the bulk optical component being such that the view of the optoelectronic device is not obscured during alignment. The visual alignment of the optoelectronic device with the bulk optical component can be performed in a gaseous environment prior to envelopment of the optical assembly with silicone because electromagnetic radiation exiting the bulk optical component does so substantially normal to the surface of the bulk optical component.